For example, when my siblings were kids we all lived in 1 house. I have 3 siblings so there were 6 of us including my parents. In 1 house.
As we graduated from college we moved out. Now there were 6 of us in 5 houses.
Beyond the raw house count, you're going to need more space. Multi-bedroom homes have shared common space. The house we grew up in had 1 dining room, 1 kitchen, 1 living room, 4 bedrooms, and 2 bathrooms.
If we each moved out on our own, we now needed a minimum of 5 dining rooms, 5 kitchens, 5 living rooms, 5 bedrooms, and 5 bathrooms.
The number of people is the same. Still just 6. But we needed more housing and more space since we didn't share common space anymore. We didn't expect more than we had before (well, beyond the practicalities - it's difficult to share a bathroom with someone you don't live with), we expected the same as we had before we moved out.